Re: cros_ec_lpcs on framework: packet too long (4 bytes, expected 0)

[Tzung-Bi Shih <tzungbi@kernel.org>]

On Tue, Jun 20, 2023 at 10:12:34AM +0200, David Rheinsberg wrote:
> Using the cros-ec over lpc device on the Framework-13, I occasionally get:
> 
>     cros_ec_lpcs cros_ec_lpcs.0: packet too long (4 bytes, expected 0)
> 
> Afterwards, the entire EC seems to be inactive and none of its controllers work, anymore (temperature sensors are stale, keyboard defunct, etc.). A reboot fixes the issues.

To be clear, does an AP reboot fix the issue?  Or does it need an EC reboot?
Will it trigger some watchdog mechanisms and thus a reboot after waiting for
a specific duration (e.g. 30 seconds)?

> I cannot trigger this issue reliably, yet it seems to happen exclusively under heavy load. Do you have any recommendations how to debug this further?
> 
> I failed tracing where the error happens and why any further functionality of the EC is disabled thereafter. Does the driver end communication on an error? Or is this likely a firmware issue and just indicative of the firmware failing?
> 
> If you have any recommendations how to enabled the cros-tracing/debug features, I'd gladly run a custom kernel for a while to see where the failure originates.

Could you get the AP and EC console log?  AFAIK, the "packet too long" is only
indicating an error of the EC command.  There should be some other error
messages directly related to the system becomes inactive.

Try to get the consoles would be the most directly helpful.  Except the logs,
ramoops, and stacktraces, for example, if the console is still available when
the issue happens, you could use SysRq to get all stack backtraces.